JERUSALEM — Israel’s cross-border clash with Iranian and Syrian forces on Saturday was a sharp escalation of long-brewing hostilities along its northern frontier — and a bracing alert to those who have focused on other areas of the Syrian civil war, on other aspects of Iran’s strategic assertiveness, or who believed that Israel’s air superiority left it invincible in its own skies.

In the space of several hours, Israel downed what it said was an Iranian drone that had penetrated its airspace, then struck back at what it called the command-and-control centre in Syria from which Iran launched the drone. An Israeli F-16, returning from the attack, crashed in northern Israel after coming under heavy Syrian anti-aircraft fire — the first Israeli jet downed under enemy fire in decades.

Israel responded with strikes against eight Syrian and four Iranian targets in Syrian territory.

Prime Minister Benjamin Netanyahu described the day’s events as proof of Israel’s resolve. “Yesterday we dealt severe blows to the Iranian and Syrian forces,” he said Sunday. “We made it unequivocally clear to everyone that our rules of action have not changed one bit. We will continue to strike at every attempt to strike at us.”

We made it unequivocally clear to everyone that our rules of action have not changed one bit. We will continue to strike at every attempt to strike at us

But strategists and military analysts in Israel did not see things quite so simply. As both sides sift through the debris, here are some important points:

A picture taken on February 10, 2018, shows the remains of a missile that landed in the southern Lebanese village of Kaoukaba, near the border with Syria, after Israel’s military attacked 12 Syrian and Iranian targets inside Syria in what it described as “large-scale” raids following an exchange of fire earlier in the day.Ali DIAALI DIA/AFP/Getty Images

This isn’t over. It’s just beginning

As the Syrian civil war winds down, a new conflict is emerging among Iran, which appears to want a lasting Syrian base to threaten Israel; Israel, which is determined to prevent this; and the government of President Bashar Assad of Syria, which showed renewed confidence in firing on Israel’s warplanes.

“We are seeing a renegotiation of the rules of the game with regard to the kind of military activity that each side tolerates in the other,” said Ofer Zalzberg, an analyst at International Crisis Group. “We will see more and more friction between the parties, given that we are seeing more and more this sense that Assad has the upper hand” against Syrian rebels.

Neither side can be expected to back down

Israel believes it is vital to stop Iran, Hezbollah or other Shiite militias from threatening it with precision rockets from faraway corners of Syria, or with artillery and troops just beyond the disputed Golan Heights.

And Iran does not want its investment in rescuing Assad to have been for naught, and to have to bring its forces home, said Giora Eiland, a former head of Israel’s National Security Council. “If Iran would move back to its bases, then Assad will have gotten what he wanted, the Russians will have gotten what they wanted — but what about them?”

Israel alone can’t stop Iran in Syria

Israel has stopped neighbouring countries from building nuclear facilities, but it has never tried to stop one from building up a conventional force, Eiland said. And it is unlikely, on its own, to succeed, even if it manages to slow down Iran’s efforts and make it be more careful in how it proceeds.

Israeli soldiers block a road in the Israeli-annexed Golan Heights, on February 10, 2018.JALAA MAREY/AFP/Getty Images

What Israel can do, Eiland said, is punish the Assad government for Iran’s buildup.

“We destroyed some Syrian targets, and that might create some tension between Bashar Assad and the Iranians,” Eiland said. “Assad is not interested in the Iranian presence; he just cannot say no to it. But if he and his regime are paying more of a price, maybe he can ask Iran to stop, or lean on the Russians to help.”

With the Trump administration looking to reopen the nuclear deal with Iran, Eiland said, Israel could try to bring its own security concerns into the mix of a new negotiation.

“The Americans and Europeans want to prevent Iranian long-range missiles from reaching Europe,” he said. “But from the Israeli point of view, Iran already has missiles that can cover Israel, so that’s much less important than Iran’s presence in Syria.”

The U.S. is focused elsewhere

The United States, Israel’s most important ally, has focused on defeating the Islamic State in central and eastern Syria, not on Israel’s top concerns in the conflict. While the Trump administration on Saturday did voice its support for Israel’s right to defend itself, it has offered it no help with Iran, its proxies and the Syrian regime, Zalzberg said. “All Israelis noticed this,” he said.

Daniel B. Shapiro, a former ambassador to Israel during the Obama administration, said Saturday’s action ought to prompt the United States to begin coordinating policy, strategy and messaging with Netanyahu.

In an op-ed article Sunday in Ha’aretz, an Israeli newspaper, Shapiro noted that Secretary of State Rex Tillerson was setting out on a trip to through Jordan, Turkey, Egypt, Kuwait and Lebanon. “But oddly, Israel does not appear on the itinerary,” Shapiro wrote. “That made little sense before the Iranian incursion yesterday. It would be malpractice now.”

If you are committed to countering Iran in the region then you must do so in Syria — first

Chagai Tzuriel, director general of the Israeli Intelligence Ministry, said the United States needed to heed Israel’s warnings about Iran’s intentions in Syria. Iran, he said, was the “master of the slippery slope.”

“If you are committed to countering Iran in the region then you must do so in Syria — first,” he said, adding: “I’m not giving up on the U.S.”

Russia can’t stay neutral for long

Russia has played its hand expertly in Syria up until now, Israeli strategists say. It has cooperated with Iran in aiding the Assad regime, but also has communicated closely with the Israelis, allowing Israel to act militarily against the two. But intensifying conflict could make it difficult for Russia to retain that detachment.

“I believe the Russians want a ‘Pax Russiana’ to stabilize their achievements — and their achievements are formidable,” said Tzuriel, the Israeli intelligence official. “I think they understand that the presence of Iranian military and Shiite militia in Syria has the potential to destroy all their gains. They don’t want that.”

Zalzberg said Russia had been something of a “frenemy” to both Israel and Iran so far, but now faced “a huge dilemma.”

“Assad knows that Russia has advanced anti-aircraft capacities in Syria that it hasn’t deployed to protect him,” he said. “And Israel knows that Russia hermetically controls Syrian airspace, and yet it did not inform Israel about the drone. Russia is going to have to decide which side they are on — and they don’t want to be seen as being on either side.”

There was much keening in the Israeli press over Saturday’s biggest surprise: that an Israeli F-16 could be lost during a combat mission — the first known such incident since 1982.

Israelis had “grown accustomed to no one in the region being able to threaten our aircraft,” Alon Ben-David wrote in Maariv, a newspaper. Now, he said, “Assad’s men will try hard to achieve more accomplishments like this.”

And Amos Yadlin, a former Israeli air force pilot who leads the Institute for National Security Studies in Tel Aviv, said it was “crucial that we learn why a plane with such advanced capabilities was downed by such an old-generation missile.”

But Yadlin, writing in the Yedioth Ahronoth newspaper, said that celebrations in Damascus were misguided. Israel showed intelligence superiority in striking Iranian forces, and air supremacy in destroying Syrian air-defense installations, he wrote.

“There are uncertainties, surprises and mistakes in every battle that come with a cost,” he wrote.